Natural human aging processes include wrinkle formation, skin flaccidity and skin darkening, which gradually appear with aging. The layers of skin from top to bottom are the epidermis, dermis, and hypodermis. The causes of skin aging can be classified into endogenous and exogenous factors. Endogenous aging is a natural aging process of the human body, including cell apoptosis, hormone decrease, and weakened immunity. The decrease of hormone secretion may slow skin metabolism and gradually reduce the production of collagen and elastin due to the deterioration of fibroblast function in the dermis. As a result, the connective tissues in the dermis deteriorate, leading to skin flaccidity, and even wrinkling. Furthermore, the deterioration of the connective tissues in the dermis may decrease the water storage function of the skin, leading to skin dryness and water deficiency, etc.
Exogenous aging is caused by extrinsic factors, such as sunshine, pollution, free radicals, and smoking. The factor that damages the skin most and accelerates the aging of skin is ultraviolet (UV) rays from the sun. Based on the wavelength, ultraviolet (UV) rays can be classified into long wavelength UV (UVA), medium wavelength UV (UVB), and short wavelength UV (UVC). UV rays that people are most exposed to in daily life are UVA and UVB, which may cause erythema, sunburns, damage to the deoxyribonucleic acid (DNA) in skin cells, abnormality of the skin immune system, and skin cancer. The aging phenomenon caused by UV rays is called “photo-aging,” which may increase the amount of matrix metalloproteinase (MMP) in the dermis via the phosphorylation of the mitogen-activated protein kinase (MAP Kinase) pathway. Matrix metalloproteinase may decompose collagen to reduce the collagen content in the skin. Furthermore, UV rays may promote the formation of reactive oxygen species (ROS), such as oxygen ions, peroxides, organic and inorganic radicals, etc, and cause denaturing of the collagen and loss of collagen function. Without the support of collagen, the skin becomes flaccid, and cuticula may overgrow, leading to darkened skin.
Currently known animal collagen can be classified approximately into 21 type, in which different kinds of collagen exist in different tissues. Out of all the collagen in skin tissue, Type I collagen is the most abundant (80% of skin collagen) and has the most functions. Type III collagen comprises about 20% of the skin collagen. Fibroblasts in the dermis mainly produce Type I collagen and Type III collagen for the skin.
As described above, matrix metalloproteinase may decompose collagen to reduce the collagen content in the skin, while reactive oxygen species will cause collagen to lose its function. Thus, if the oxidation reaction of the reactive oxygen species or the activity and/or expression of matrix metalloproteinase can be inhibited, then the effects of improving/caring for skin quality can be achieved.
It has been found that the expression of matrix metalloproteinase-1 can be inhibited by ziyuglycoside-I obtained by extracting the roots of Sanguisorba officinalis with 70% ethanol. The expression of matrix metalloproteinase-1 can also be inhibited by sumaflavone and amentoflavone obtained by extracting Selaginella tamariscina with methanol. However, there is still a need to find components that have better effects of inhibiting the activity of matrix metalloproteinase.
The inventors of the present invention discovered that a Flemingia macrophylla extract has excellent effects of anti-oxidation, inhibiting the activity of matrix metalloproteinase, inhibiting the expression of matrix metalloproteinase, and/or inhibiting the phosphorylation of mitogen-activated protein kinase. Thus, the extract can be used in the improvement, care, and/or repair of skin.